Method for producing frp

ABSTRACT

A method of producing FRP includes disposing a preform made of a reinforcing fiber base material in a cavity of a mold, providing a resin injection path and a suction path that sucks at least air to the mold, and causing resin from the resin injection path to flow in a direction toward the suction path in the cavity to be impregnated into the preform, wherein 1) a high flow resistance region for partially making the resin flowing in the preform hardly flow is formed in the preform itself, 2) a flow front of the resin flowing in the direction toward the suction path through the high flow resistance region is controlled to settle within a permitted region that has been predetermined relative to a shape of a product to be molded, 3) the resin injection path is formed from a runner provided around the preform and the suction path is disposed at a central portion of the preform, and the high flow resistance region is formed at a corresponding part corresponding to a part around the suction path as a high flow resistance region to cause the resin flowing in the preform from a part around the corresponding part toward the corresponding part hardly flow at the corresponding part.

TECHNICAL FIELD

This disclosure relates to a method of producing FRP (Fiber ReinforcedPlastic), and specifically, to improvement of a method of producing FRPby impregnating an injected resin into a preform made of a reinforcingfiber base material by RTM (Resin Transfer Molding) method.

BACKGROUND

An RTM method which is a so-called “RTM multi-point injection method” isknown wherein a preform made of a reinforcing fiber base material isdisposed in a cavity of a mold, and a resin is injected from a pluralityof resin injection ports facing one surface of the preform to impregnatethe resin into the reinforcing fiber base material of the preform (forexample, JP-A-2010-89501). Further, an RTM method which is a so-called“line injection method” is also known wherein a resin injection lineextending along an end surface of a preform is provided at an endsurface side of the preform, and a resin is supplied and injected fromthe end surface of the preform disposed in a cavity.

In the above-described multi-point injection method, as compared to theline injection method, because the resin can be spread in all directionsfrom each of many injection points disposed on one surface of thepreform, it has an advantage excellent in high-speed impregnationproperty. Further, since injection points are disposed on one surface ofthe preform, without being greatly influenced by a peculiar flow such asa race-tracking (a phenomenon wherein resins having flowed fromdifferent directions regulate their flows to each other and astripe-like residence portion is formed), that is liable to occur at aposition around a preform, the injected resin from each of therespective injection points can be spread in a flow front shape (a shapeof a tip portion of a resin flow) in accordance with the resistance ofthe preform or in a flow front shape corresponding to the shape of aninjection port (for example, in the case of a circular injection port, aconstant-thickness preform or a quasi-isotropic laminated preform, acircular flow front shape is likely formed). However, because it is amethod of injecting a resin into a closed mold, an air trap is liable tooccur within a region of a product to be molded, but, for such a case, amethod of assisting the resin injection and impregnation by vacuumsuction is also introduced.

On the other hand, in the line injection method, because resin isinjected from a predetermined resin injection line in a specifieddirection, the resin injection speed can be controlled relativelyeasily, and the position of a flow front and the degree of the progressthereof can be monitored also easily. However, if the line of the shapeof the flow front does not progress in a desired shape or if thereoccurs a place hardly reached with the flow front, a portion lacking inimpregnated resin (resin starving portion or resin non-impregnatedportion) is liable to be generated, and further, there is a fear that aportion which is not sufficiently favorable in surface quality isgenerated.

However, even in any of the above-described multi-point injection methodand line injection method, a race-tracking is still liable to occuraround a preform, and there remains a fear that resin first flows aroundthe outer circumferential portion of a preform and air is trapped in aproduct. If air is trapped in a product, a resin starving portion or aresin non-impregnated portion is liable to be generated and, further,there is a fear that a portion which is not sufficiently favorable insurface quality is generated.

For example, in the above-described RTM multi-point injection method,there is a case where the following problem may occur. The flow frontshape depending upon the resistance of a preform or the shape of a resininjection port does not always coincide with the shape of a moldedproduct to be molded. Therefore, there is a case where an air trap iscaused within the product by race-tracking and the like. Further, in themethod of assisting by vacuum suction, frequently a sufficient timecannot be taken to completely create a vacuum condition, from thebalance with a molding cycle time. Therefore, in particular, in the caseof a large mold (cavity), there is a case where the molding finishes ata condition where air is finally trapped. Furthermore, as a method ofreducing air traps, although there is a method of sucking and evacuatingair and resin together (because it is difficult to separate them, as theresin contains bubbles), cleaning an evacuation port is troublesome and,therefore, it involves another problem.

Accordingly, paying attention to the above-described limits inconventional technologies, there is a need to provide a method ofproducing FRP using RTM method, capable of obtaining a molded productfavorable in quality with no air traps, in particular, capable ofobtaining a molded product with no air traps by using a completelyclosed mold.

SUMMARY

We provide a method of producing FRP in which a preform made of areinforcing fiber base material is disposed in a cavity of a mold, aresin injection path and a suction path that sucks at least air areprovided to the mold, and resin from the resin injection path is causedto flow in a direction toward the suction path in the cavity to beimpregnated into the preform, wherein a high flow resistance region forpartially making the resin flowing in the preform hardly flow is formedin the preform itself, and a flow front of the resin flowing in thedirection toward the suction path through the high flow resistanceregion is controlled to settle within a permitted region that has beenpredetermined relative to a shape of a product to be molded.

We also provide a method of producing FRP including disposing a preformmade of a reinforcing fiber base material in a cavity of a mold,providing a resin injection path and a suction path that sucks at leastair to the mold, and causing resin from the resin injection path to flowin a direction toward the suction path in the cavity to be impregnatedinto the preform, wherein 1) a high flow resistance region for partiallymaking the resin flowing in the preform hardly flow is formed in thepreform itself, 2) a flow front of the resin flowing in the directiontoward the suction path through the high flow resistance region iscontrolled to settle within a permitted region that has beenpredetermined relative to a shape of a product to be molded, 3) theresin injection path is formed from a runner provided around the preformand the suction path is disposed at a central portion of the preform,and the high flow resistance region is formed at a corresponding partcorresponding to a part around the suction path as a high flowresistance region to cause the resin flowing in the preform from a partaround the corresponding part toward the corresponding part hardly flowat the corresponding part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic vertical sectional view of an RTM apparatus usedfor carrying out our method according to a first example, and asectional view as viewed along B-B line of FIG. 2.

FIG. 2 is a schematic perspective plan view of an interior of a mold ofthe apparatus depicted in FIG. 1 as viewed from the upper surface sideof the mold.

FIG. 3 is an enlarged partial sectional view as viewed along A-A line ofFIG. 2.

FIGS. 4(A) to 4(E) are schematic plan views showing steps of spreadingof an injected resin in the mold depicted in FIG. 2.

FIG. 5 is a schematic plan view showing an example of spreading state ofan injected resin in a conventional mold for comparison.

FIG. 6 is a schematic vertical sectional view of an RTM apparatus usedfor carrying out our method according to a second example, and asectional view as viewed along B-B line of FIG. 7.

FIG. 7 is a schematic perspective plan view of an interior of a mold ofthe apparatus depicted in FIG. 6 as viewed from the upper surface sideof the mold.

FIG. 8 is an enlarged partial sectional view as viewed along A-A line ofFIG. 7.

FIGS. 9(A) to 9(D) are schematic plan views showing steps of spreadingof an injected resin in the mold depicted in FIG. 7.

EXPLANATION OF SYMBOLS

-   1: RTM apparatus-   2: cavity-   3: mold-   4: upper mold-   5: lower mold-   6: press mechanism-   7: preform-   8: resin supplying path-   9: resin injection port-   10: valve body-   11: heat medium circulation path-   12: seal material-   21: outline of product-   22: high flow resistance region-   23: air trap region-   24: distance-   25: suction port-   26: flow path reduced part-   27: resin detecting sensor-   28: valve body-   31: flow front-   32: trapped air compression part-   101: RTM apparatus-   102: cavity-   103: mold-   104: upper mold-   105: lower mold-   106: press mechanism-   107: preform-   108: runner-   109: suction port-   110: resin injection port-   111: valve body-   112: seal material-   113: heat medium circulation path-   121: high flow resistance region-   122: outer circumference part of preform-   123: outline of product-   124: resin detecting sensor-   131: flow front-   132: non-impregnated region-   133: void region-   134: region outside product

DETAILED DESCRIPTION

We thus provide a method of producing FRP in which a preform made of areinforcing fiber base material is disposed in a cavity of a mold, aresin injection path and a suction path for sucking at least air areprovided to the mold, and resin from the resin injection path is causedto flow in a direction toward the suction path in the cavity to beimpregnated into the preform, and is characterized in that a high flowresistance region to partially cause the resin flowing in the preformhardly flow is formed in the preform itself, and a flow front of theresin flowing in the direction toward the suction path through the highflow resistance region is controlled to settle within a permitted regionthat has been predetermined relatively to a shape of a product to bemolded.

In such a method of producing FRP to add an improvement to theaforementioned RTM multi-point injection method, for example, astructure can be employed wherein the above-described resin injectionpath is formed from a plurality of resin injection ports opened facingone surface of the preform disposed in the cavity, the high flowresistance region is formed as a high flow resistance region topartially make the resin flowing in the preform from an inside part ofthe preform toward an outer circumference part of the preform hardlyflow to extend along the outer circumference part of the preform at aposition outside a molded product relatively to an outline of theproduct to be molded (a method for producing FRP according to a firstexample). By such a structure, it becomes possible to control the flowfront of the resin to settle within the permitted region predeterminedrelatively to the shape of the product to be molded.

Further, to add an improvement to the aforementioned line injectionmethod, for example, a structure can be employed wherein theabove-described resin injection path is formed from a runner providedaround the preform and the above-described suction path is disposed at acentral portion of the preform, and the high flow resistance region isformed at a corresponding part corresponding to a part around thesuction path as a high flow resistance region to cause the resin flowingin the preform from a part around the corresponding part toward thecorresponding part hardly flow at the corresponding part (a method forproducing FRP according to a second example). Also by such a structure,it becomes possible to control the flow front of the resin to settlewithin the permitted region predetermined relatively to the shape of theproduct to be molded. In this case of the second structure, theabove-described high flow resistance region is formed basically at aposition outside a molded product relative to an outline of the productto be molded or at a position where an appearance design property is notrequired in the product to be molded.

In the above-described matter, a preferable range of a degree ofhardness in resin flow in the high flow resistance region can beexpressed, for example, by permeability. With respect to thepermeability that is an impregnation property of a resin into areinforcing fiber base material, it is known that it can be generallyexpressed by the following equation:

l=(∈/(1−∈))√(αP/2)×∫[dt/√(μ(t)t]

-   -   l: permeability, ∈: resistance of base material, α: constant,    -   P: vacuum pressure in base material, μ(t): viscosity, t: passed        time.

The permeability corresponds to a distance (thickness) in which theresin is impregnated into the reinforcing fiber base material. When theabove-described hardness in resin flow in the high flow resistanceregion is expressed by the permeability, the permeability in the highflow resistance region is preferably 0.8 time or less relative to thepermeability in a part within the range of a product to be molded, morepreferably 0.5 time or less.

In the method of producing FRP according to the above-described firstexample, the high flow resistance region of partially causing the resinhardly flow by increasing the flow resistance of the resin is formed inthe preform itself, and the high flow resistance region is formed toextend along the outer circumference part of the preform at a positionoutside the product relatively to the outline of the product to bemolded. Each flow front of the resin injected from each injection pointof the plurality of the resin injection ports is likely to spread in ashape of a circle or the like at an initial stage and, then, is likelyto spread toward the outer circumference part of the preform at a stateof an indefinite shape formed by joining of respective spread flowfronts or at a state of the circular shape or the like partiallymaintained.

Shortly, when a part of the flow front reaches the above-described highflow resistance region, because the resin flow resistance rapidlybecomes great at the reached portion, at that portion spreading of theflow front is once suppressed. Succeedingly, the flow front in anadjacent region which has not yet reached the high flow resistanceregion is likely to spread toward the outer circumference part of thepreform, successively reaches the high flow resistance region and,similarly to in the above-described manner, because the resin flowresistance rapidly becomes great at the portion reached to the high flowresistance region, at that portion spreading of the flow front is oncesuppressed. As a result of such behaviors of resin flow performedsuccessively, the resin spread from the inside part of the preformtoward the outer circumference part of the preform is filled (spread) atleast over the whole of the range of the region of the product to bemolded among the range surrounded by the high flow resistance region,and air (bubbles) involved at the process of the resin spreading issuccessively pushed out to the side of the high flow resistance regionpositioned outside the range of the product.

As a result, the injected resin is favorably impregnated into thereinforcing fiber base material of the preform over the entire region ofthe product to be molded without causing air to be involved and, whilethe advantage of excellent high-speed impregnation property due to RTMmulti-point injection method is served as it is, it becomes possible toobtain a desirable molded product with no air traps. Although theabove-described high flow resistance region is provided to the preformitself, because this high flow resistance region is formed at a positionoutside the product to be molded, it may be removed after apredetermined molding. Although by this re-moval the yield of thematerial may be slightly reduced, the advantages, much greater thanthat, of an excellent quality with no air traps and a shortened cycletime for molding ascribed to an excellent high-speed impregnationproperty of the multi-point injection method can be obtained.

However, since the high flow resistance region is formed at a positionoutside the product to be molded, it is preferred to suppress the areatherefor to a minimum from the viewpoint of the yield of the materialand the like. On the other hand, as long as the high flow resistanceregion can be provided around the product, it is considered to be amolding method in which it is not necessary to arrange the end part ofthe base material by cutting. Therefore, it is preferred from the pointthat a process of arranging the end part by cutting is unnecessary and aproduct can be molded at a stable condition.

In the method of producing FRP according to the above-described firstexample, it is preferred that an air trap region to suck air dischargedthrough at least the high flow resistance region is formed by the moldat a position outside the high flow resistance region of the preform toextend along the high flow resistance region. If the air trap region isthus formed at an outer circumference side of the high flow resistanceregion, although spreading the flow front of the resin is oncesuppressed at the high flow resistance region as aforementioned, sincethe air pushed out together with the resin is more flowable compared tothe resin, the air is sent to or sucked by the air trap region throughthe high flow resistance region. Therefore, air is further hardly leftwithin the range of the product to be molded, and the quality of themolded product can be further improved.

The volume of the above-described air trap region is preferably 0.1 timeor more and 50 times or less relative to a space volume within theproduct. Further preferably, it is desired that the above-describedvolume is 0.1 time or more and 2 times or less relative to a spacevolume after compression when the space volume is compressed by theresin injection pressure. In the case where the space is sacked byvacuum, the above-described volume may be reduced by the ratiocorresponding to the vacuum suction. Although at least air may betrapped at this air trap region (namely, at a position irrelevant to themolded product), more preferably, trapped air is sucked and removed froma suction port opened at an appropriate position of the air trap region.

Further, it is preferred that a flow path reduced part to cause resin tohardly flow when resin is discharged through the high flow resistanceregion is formed by the mold at a position provided with a suction portopened to the air trap region or its vicinity. Namely, even if there isa case where resin flows up to a position near the suction port of theair trap region, it is suppressed that the resin is sucked into thesuction port, by the flow path reduced part without greatly reducing theair suction performance. The suction port is preferably disposed within50 cm² from a position farthest from the resin injection port.Furthermore, in a portion near the suction port, to form theabove-described flow path reduced part, the thickness of the cavity ispreferably small. This cavity thickness is determined, for example, tosatisfy the following equation:

2.5×10⁻⁶ mm<t ² /L

-   -   t<t′    -   t (mm): cavity thickness at a position near suction port    -   t′ (mm): cavity thickness at a position other than a position        near suction port    -   L (mm): minimum distance from a position near suction port to a        position other than a position near suction port.

By such a setting, it is possible to reduce air in the mold efficientlyand as much as possible.

Further, it is preferred that a resin detecting sensor is disposed at aposition near the above-described suction port. When resin is dischargedthrough the high flow resistance region, the resin is detected at aposition near the position provided with the suction port. In such astructure, it becomes possible to stop the impregnation withoutdischarging the resin from the suction port.

Further, the above-described high flow resistance region can be formedby reducing the thickness of the outer circumference part of the preformby the mold at the position outside the molded product relatively to theoutline of the product to be molded, and can also be formed by enhancingthe density of arrangement of reinforcing fibers in the outercircumference part of the preform in advance at the position outside themolded product relatively to the outline of the product to be molded.

Further, a method can be employed wherein the plurality of resininjection ports are configured to be controlled by opening/closingindependently from each other, and the timing to open respective resininjection ports is controlled so that flow fronts of resin injected fromthe respective resin injection ports reach the high flow resistanceregion substantially simultaneously. Namely, in the case where there aremany resin injection points, the timing of opening the injection portsis controlled so that the resins injected from substantially all theinjection points reach the above-described high flow resistance region,being hardly flowed, simultaneously. By such a control, it becomespossible to perform desired resin injection and impregnation at aminimum resin injection amount.

In the above-described method of producing FRP according to the secondexample, a runner to inject resin is provided around the preform andfrom the runner the resin is injected from the portion around thepreform toward the central portion of the preform. The suction path isdisposed at a central portion of the preform and the high flowresistance region of partially causing the resin to hardly flow bymaking the flow resistance of resin greater is formed in the preformitself around the suction path. The resin injected from the runner flowstoward the suction path disposed in the central part of the preform andthe flow front of the injected resin also flows toward the suction path.Shortly, when a part of the flow front reaches the above-described highflow resistance region formed around the suction path, because the flowresistance of the resin rapidly becomes great at the reached portion, atthat portion spreading of the flow front is once suppressed.Succeedingly, the flow front in an adjacent region which has not yetreached the high flow resistance region is likely to spread toward thehigh flow resistance region formed around the suction path, successivelyreaches the high flow resistance region, and similarly to in theabove-described manner, because the resin flow resistance rapidlybecomes great at the portion reached to the high flow resistance region,at that portion spreading of the flow front is once suppressed.

As the result of such behaviors of resin flow performed successively, inthe resin spread from the outer circumference part of the preform towardthe inside part of the preform, the whole of the flow front reaches atleast the high flow resistance region, and for the region of the preformother than the region surrounded by the high flow resistance region, theinjected resin is filled (spread) sufficiently over the whole of theregion, and air (bubbles) involved at the process of the resin spreadingis successively collected within the range surrounded by the high flowresistance region, namely, collected to the part provided with thesuction path. As a result, the injected resin is favorably impregnatedinto the reinforcing fiber base material of the preform over the entireregion of the target preform region without causing air to be involved,and it becomes possible to obtain a desirable molded product with no airtraps. Although the above-described high flow resistance region isprovided to the preform itself, because, as aforementioned, this highflow resistance region is formed basically at a position outside theproduct to be molded, or at a position which does not require anappearance design property in the product to be molded, it does notbecome a problem, and it may be left as it is or it may be removed asneeded after molding. However, it is preferred to suppress the area ofthe high flow resistance region to a minimum area from the viewpoint ofthe yield of the material and the like. In the case of the high flowresistance region provided outside the product, the quality of themolded product can also be improved by introducing a medium (same resin,resin cured more early than the injected resin, or compressible resin)from the suction path.

In the above-described method of producing FRP according to the secondexample, it is preferred that the resin having flowed into the high flowresistance region is detected at a position near the portion providedwith the suction path. In such a structure, it becomes possible to stopthe impregnation without discharging the resin from the suction port. Asthe resin detecting sensor, for example, a dielectric-type sensor, asensor using an optical fiber, a pressure sensor and the like can beused.

Further, the above-described high flow resistance region can be formedby reducing the thickness of the preform at the high flow resistanceregion by the mold, and can also be formed by enhancing the density ofarrangement of reinforcing fibers in the preform at the position of thehigh flow resistance region in advance.

Further, in the above-described methods of producing FRP according tothe first and second examples, a method can also be employed wherein thepreform is formed from a laminate of a plurality of reinforcing fiberbase materials, and the resin flow resistance of a reinforcing fiberbase material of an inner layer is set to be lower than that of areinforcing fiber base material of a surface layer. Namely, a layerexhibiting a good flow is put in as an intermediate layer of thepreform. In this layer exhibiting a good flow, it is preferred that theaverage value of the permeability thereof is better than that of theabove-described high flow resistance region exhibiting a bad flow by 10times or more. More preferably, it is better by 50 times or more.Further, it is preferred that the permeability of the intermediate layerof the preform is better than that of the surface layer by 1.5 times ormore. More preferably, it is better by 2 times or more. By such astructure, it becomes possible to store air in the interior as much aspossible without discharging it to the outer surface side as much aspossible. The air in the interior is pushed out to the side of theportion provided with the suction path through the above-describedintermediate layer exhibiting a good flow.

Furthermore, it is also preferred that the thickness of the preform inthe area within the product to be molded before being disposed is set tobe greater than the height of a corresponding part of the cavity. Forexample, the thickness of the preform is set to be greater than theheight of the cavity by 0.5% or more and 20% or less at a rate convertedinto volume content of reinforcing fibers. In such a manner, since thepreform is pressed by an appropriate pressing force from both surfacesides by closing of the mold and the preform becomes a state compressedslightly, the inner surface of the mold and the surface of the preformare tightly contacted to each other at a good condition, and even in thecase where a small amount of air is contained in the injected resin fromthe resin injection path, it becomes possible to suppress the containedair or the resin containing air to run on the surface of the preform,and it can contribute to improvement of the surface quality of themolded product.

Thus, in our method of producing FRP, it becomes possible to obtain amolded product having a high quality which does not cause an undesiredair trap. In the method of producing FRP according to a first example,while an advantage excellent in high-speed impregnation property due toRTM multi-point injection method is served substantially as it is and ahigh productivity is maintained, by forming the high flow resistanceregion at a position of the preform itself outside the product relativeto the outline of the product to be molded, it becomes possible toobtain a high-quality molded product with no undesired air traps withinthe range of the product. In particular, by forming the air trap regionat a position outside the high flow resistance region and adequatelysucking and removing the air discharged, a further high-quality moldedproduct can be obtained efficiently.

Further, in the method of producing FRP according to a second example,the resin injected from the runner can be intentionally controlled to adesirable flow to make the flow front thereof reach the high flowresistance region over the entire flow front, and it becomes possible toobtain a high-quality molded product with causing no undesired air trapswithin the region of the preform to be made as a product.

Hereinafter, examples will be explained referring to the figures.

FIG. 1 shows an example of an RTM apparatus used for carrying out amethod according to a first example. In FIG. 1, RTM apparatus 1 has anupper mold 4 and a lower mold 5 as a mold 3 to form a cavity 2, and theupper mold 4 is closed and opened by a press mechanism 6. In cavity 2, apreform 7 composed of a laminate of reinforcing fiber base materialsand, for example, formed in a predetermined shape in advance isdisposed. At a condition where this preform 7 is disposed in cavity 2,upper mold 4 is closed relatively to lower mold 5, a resin to form anFRP is supplied from a resin supplying path 8, and the resin is injectedinto the cavity 2 from resin injection ports 9 as a plurality of resininjection paths opened facing one surface (upper surface) of the preform7, and impregnated into the reinforcing fiber base materials forming thepreform 7. Resin injection port 9 is opened/closed by, for example, apin-like valve body 10, and the circumference of cavity 2 is sealed by aseal material 12. Mold 3 is heated and cooled by, for example, a heatmedium circulated in a heat medium circulation path 11, at the time ofresin injection, it is heated and a favorable resin impregnation isattempted and, after the resin impregnation, it is cooled (possible bynatural heat radiation) and the resin having been injected andimpregnated is cured to make a predetermined FRP molded product.

The plurality of resin injection ports 9 are disposed as a plane viewsuch as shown in FIG. 2 relative to one surface of preform 7. As a planeview, preform 7 is formed greater than an outline 21 of a product to bemolded and, in this preform 7 itself, a high flow resistance region 22to partially make the resin spreading from the inside part of thepreform 7 (a region inside the outline 21 of the product) toward theouter circumference part of the preform 7 hardly flow is formed toextend along the outer circumference part of the preform 7 at a positionoutside the product relatively to the outline 21 of the product to bemolded. In this example, as shown in FIG. 3, this high flow resistanceregion 22 is formed by reducing the thickness of the outer circumferencepart of preform 7 by mold 3 (upper mold 4 and lower mold 5) at aposition outside the molded product relatively to outline 22 of theproduct. However, as aforementioned, the high flow resistance region canalso be formed by enhancing the density of arrangement of reinforcingfibers in the outer circumference part of the preform in advance at aposition outside the molded product relatively to the outline of theproduct.

As shown in FIGS. 2 and 3, an air trap region 23 to suck air dischargedthrough at least high flow resistance region 22 is formed by mold 3 at aposition outside the high flow resistance region 22 to extend along thehigh flow resistance region 22. Relative to this air trap region 23, ata position farthest from any of a plurality of resin injection ports 9,for example, at a position away from that by a distance 24, a suctionport 25 as a suction path is provided, and a flow path reduced part 26to make resin hardly flow when resin is discharged through high flowresistance region 22 is formed by mold 3 at a position provided with thesuction port 25 or its vicinity (FIG. 3). It is preferred that near thisposition provided with suction port 25, a resin detecting sensor 27 todetect the resin when the resin is discharged through high flowresistance region 22 is provided near this position provided withsuction port 25. It is possible to control the suction from suction port25, for example, as shown in FIG. 3, by the opening/closing operation ofa pin-like valve body 28.

Further, although it is not shown in the figures, a structure can alsobe employed wherein the plurality of resin injection ports 9 areconfigured to be controlled with opening/closing independently from eachother, and a controller that controls the opening timing of each resininjection port 9 is provided so that the tips of the flows (flow fronts)of the resins injected from respective resin injection ports 9 reachhigh flow resistance region 22 substantially simultaneously.

In our method of producing FRP carried out by using thus constructed RTMapparatus 1, the flows of the resins injected from the respective resininjection ports 9 progress, for example, as shown in FIG. 4(A) to (E).As shown in FIG. 4(A), when the resin injection from the respectiveresin injection ports 9 is started, flow front 31 of each injected resinspreads at a circular shape. Shortly, parts of the respective flowfronts 31 are joined to each other, the condition reaches the stateshown in FIG. 4(C) through the state shown in FIG. 4(B). When the partof the flow front 31 of the resin flow which is likely to spread towardthe outer circumference part of preform 7 reaches high flow resistanceregion 22, at the reached portion the flow resistance of the resinrapidly becomes great, the spreading of the flow front 31 is oncesuppressed. This suppressing state successively progresses in thedirection in that the high flow resistance region 22 extends, shortly asshown in FIG. 4(D), the resin flow progresses over the entire region atleast within the outline 21 of the product, further up to the part overmost of the high flow resistance region 22, and furthermore over thepart except the portion near suction port 25 of air trap region 23. Whenthe spreading of flow front 31 progresses up to the portion near suctionport 25, suction of the suction port 25 may be stopped. Even if it isstopped, because a negative pressure due to the suction up to that timeremains, as shown in FIG. 4(E), a trapped air compression part 32 isgenerated, and the resin is delivered sufficiently up to a partimmediately near the suction port 25.

In the above-described steps of the spreading of flow front 31 in theresin flow, the resin being spread from the inside part of preform 7toward the outer circumference part of the preform 7 is filledsufficiently well at least over the whole of the range of the region ofthe product to be molded and impregnated into the reinforcing fiber basematerial of the preform 7, and accompanying to the resin spreading, airinvolved in the preform 7, further, even air (bubbles) mixed in theresin, is pushed out successively toward the side of high flowresistance region 22 positioned outside the range of the product and,further, to air trap region 23. Therefore, the injected resin isimpregnated well into the reinforcing fiber base material of the preformwithout causing air to be involved, selectively over the entire regionof the product to be molded and, while the advantage of excellenthigh-speed impregnation property due to RTM multi-point injection methodis served as it is and shortening of the molding cycle time can beachieved, it becomes possible to obtain a desirable molded product withno air traps. After predetermined molding, high flow resistance region22 having been provided outside the outline 21 of the product may beremoved as needed together with the resin impregnated thereinto.

In FIG. 5, for comparison, shown is an example of spreading of a flowfront 43 of the resin injected from a resin injection port 42 providedrelatively to a preform 41 in a conventional RTM process. Even withinthe region of the product, an air trap region 43 may be generated in aportion which the resin is hardly delivered, or undesired air flow asshown by the arrows may occur, and air is likely to be trapped in themolded product.

FIG. 6 shows an example of an RTM apparatus used to carry out a methodaccording to a second example. In FIG. 6, RTM apparatus 101 has an uppermold 104 and a lower mold 105 as a mold 103 to form a cavity 102, andthe upper mold 104 is closed and opened by a press mechanism 106. Incavity 102, a preform 107, composed of a reinforcing fiber basematerial, for example, composed of a laminate of reinforcing fiber basematerials and, for example, formed in a predetermined shape in advance,is disposed. At a condition where this preform 107 is disposed in cavity102, upper mold 104 is closed relatively to lower mold 105, a resin toform an FRP is injected from a runner 108 provided around the preform107 toward the preform 107, a suction port 109 as a suction path isprovided relatively to cavity 102, and the injected resin is impregnatedthrough the suction into the reinforcing fiber base material forming thepreform 107. Supply of the resin to runner 108 is performed through aresin injection port 110 (shown in FIG. 7) opened at an appropriateposition of the runner 108. Suction port 109 is opened/closed by, forexample, a pin-like valve body 111 and, relative to cavity 102, thecircumference of runner 108 is sealed by a seal material 112. Mold 103is heated and cooled by, for example, a heat medium circulated in a heatmedium circulation path 113, at the time of resin injection, it isheated and a favorable resin impregnation is attempted and, after theresin impregnation, it is cooled (possible by natural heat radiation)and the resin having been injected and impregnated is cured to make apredetermined FRP molded product.

For example, the planar disposition is shown in FIG. 7, theabove-described suction port 109 is disposed at a central part ofpreform 107 and a part of the preform 107 itself (a corresponding part)corresponding the part around the suction port 109 is formed as a highflow resistance region 121 to partially make the resin flowing from theportion around the corresponding part toward the corresponding parthardly flow at the corresponding part. This high flow resistance region121 is formed at a position outside the product relatively to theproduct to be molded or at a position where an appearance designproperty is not required in the product to be molded and, in thisexample as shown in FIG. 8, it is formed by partially reducing thethickness of the preform 107 in the region of the product by mold 103(upper mold 104 and lower mold 105) at the high flow resistance region121. However, as aforementioned, the high flow resistance region canalso be formed by enhancing the density of arrangement of reinforcingfibers in the preform in advance at a position of the high flowresistance region.

In this example, an outline 123 of the product to be molded is setwithin an outer circumference part of preform 122, and theabove-described runner 108 is provided around the preform 107 to extendalong the outer circumference part of preform 122 over the entirecircumference. To runner 108, as described above, the resin is suppliedfrom resin injection port 110 opened at an appropriate position of therunner 108. Further, at a position near the position provided withsuction port 109 in high flow resistance region 121, a resin detectingsensor 124 to detect the resin having flowed into the high flowresistance region 121 is provided.

In the method of producing FRP carried out by using thus constructed RTMapparatus 101, the resin supplied from the respective resin injectionports 110 into runner 108 is injected from the runner 108 toward preform107 from the circumference part of the preform 107, while being flowedin the runner 108. The flow of this injected resin progresses, forexample, as shown in FIG. 9(A) to (D). As shown in FIG. 9(A), when theinjection from runner 108 toward preform 107 from the circumference partof the preform 107 is started, the shape of flow front 131 indicatingthe tip portion of the flow of the injected resin spreads from the outercircumference part of preform 122 toward the inside part of the preform107. The region inside this flow front 131 shows a resin non-impregnatedregion 132 and, accompanying the progress of the flow front 131 as shownin FIG. 9(B), the non-impregnated region 132 is gradually narrowed in anindefinite shape. Shortly, a part of flow front 131 reaches high flowresistance region 121, at the reached portion the flow resistance of theresin rapidly becomes great, and the spreading of the flow front 131 issuppressed. Parts of flow front 131 which have not yet reached high flowresistance region 121 successively reach the high flow resistance region121 and, shortly as shown in FIG. 9(C), the entire part of the flowfront 131 reaches the high flow resistance region 121, andnon-impregnated region 132 is settled within the range of the high flowresistance region 121. Then, when it is detected by resin detectingsensor 124 that the resin has reached a portion near suction port 109,the suction port 109 is closed by the aforementioned valve body 111 andthe injection and impregnation of the resin ascribed to the suction isstopped. Even if the suction is stopped, because a negative pressure dueto the suction up to that time remains, the flow of the resin towardsuction port 109 progresses and, as shown in FIG. 9(D), a void region133 ascribed to an air trap is reduced substantially down to the rangeof the suction port 109. Since the region including this void region 133and the above-described high flow resistance region 121 is set, forexample, as a region outside product 134, it may be removed aftermolding, or in case where it is not a problem in appearance designproperty, it may be left as it is.

In the above-described steps of the spreading of flow front 131controlled intentionally with the resin flow, the resin being spreadfrom the outer circumference part of preform 107 toward the inside partof the preform 107 is filled sufficiently well and impregnated into thereinforcing fiber base material of the preform 107 without causing airto be trapped, over the whole of the range of the region of the productto be molded or the region required with a desired surface quality inappearance and, accompanying the resin spreading, air involved in thepreform 107, further, even air (bubbles) mixed in the resin, is pushedout successively toward the side of high flow resistance region 121positioned outside the range of the above-described region, and further,to the position provided with suction port 109. Therefore, the injectedresin is impregnated well into the reinforcing fiber base material ofthe preform without causing air to be involved, selectively over thewhole of a target region of the product to be molded, and it becomespossible to achieve a desirable molded state with no air traps.

INDUSTRIAL APPLICATIONS

The method of producing FRP can be applied to any production of FRPusing RTM method. and in particular, it is suitable for mass productionrequiring to produce a molded product excellent in quality at a shortperiod of cycle time.

What is claimed is:
 1. A method of producing FRP comprising disposing apreform made of a reinforcing fiber base material in a cavity of a mold,providing a resin injection path and a suction path that sucks at leastair to said mold, and causing resin from said resin injection path toflow in a direction toward said suction path in said cavity to beimpregnated into said preform, wherein 1) a high flow resistance regionfor partially making said resin flowing in said preform hardly flow isformed in said preform itself, 2) a flow front of said resin flowing insaid direction toward said suction path through said high flowresistance region is controlled to settle within a permitted region thathas been predetermined relative to a shape of a product to be molded, 3)said resin injection path is formed from a runner provided around saidpreform and said suction path is disposed at a central portion of saidpreform, and said high flow resistance region is formed at acorresponding part corresponding to a part around said suction path as ahigh flow resistance region to cause said resin flowing in said preformfrom a part around said corresponding part toward said correspondingpart hardly flow at said corresponding part.
 2. The method according toclaim 1, wherein said high flow resistance region is formed at aposition outside a molded product relative to an outline of said productto be molded or at a position where an appearance design property is notrequired in said product to be molded.
 3. The method according to claim1, wherein resin having flowed into said high flow resistance region isdetected at a position near said portion provided with said suctionpath.
 4. The method according to claim 1, wherein said high flowresistance region is formed by reducing a thickness of said preform atsaid high flow resistance region by said mold.
 5. The method accordingto claim 1, wherein said high flow resistance region is formed byincreasing density of an arrangement of reinforcing fibers in saidpreform at a position of said high flow resistance region in advance. 6.The method according to claim 1, wherein said preform is formed from alaminate of a plurality of reinforcing fiber base materials, and resinflow resistance of a reinforcing fiber base material of an inner layeris lower than that of a reinforcing fiber base material of a surfacelayer.
 7. The method according to claim 1, wherein a thickness of saidpreform in an area within said product to be molded before beingdisposed is greater than a height of a corresponding part of saidcavity.
 8. The method according to claim 2, wherein resin having flowedinto said high flow resistance region is detected at a position nearsaid portion provided with said suction path.